This invention generally relates to a wireless telecommunications system that provides a one-to-many voice conference mode, and more specifically relates to limiting the ability of a user in a packet system that loses communication with the system in the talk mode to disrupt communications.
One example of a wireless system providing a one-to-many transmission mode is a conventional police or fire radio system. In an analog system with a single base station, a first user captures the base station by an initial transmission activated by a push to talk button. The first user's voice transmission is received by the base station and retransmitted to the other users. The transmission by the first user ends by the first user releasing the push to talk button. This allows one of the other users to reply to the first user or initiate a new transmission by activating his radio with the push to talk button. In this system a radio frequency carrier is on during the entire voice transmission. Loss of the radio frequency carrier, whether caused by the user releasing the push to talk button or by the user leaving the area of coverage, causes the base station to release its retransmission and allows another user to be able to access the system.
A wireless network that carries speech as digitized samples in packets presents additional difficulties with regard to transmission control especially where the packets are transferred from the wireless portion of the network to a wired portion of the network. This is especially apparent where the system utilizes a half-duplex transmission mode in which only one user is permitted to transmit voice communications at a time. Unlike the above example of an analog wireless system in which a radio frequency carrier was always present during a speech transmission, the speech packets carried on the wired system are decoupled from the wireless portion of the system and hence information concerning the status of wireless communications link is normally not available at packet nodes in the wired system. A packet based system having both a wireless and wired portion typically relies upon an end of transmission signal transmitted from the active (talking) user at the end of voice transmission such as initiated by the release of a push to talk button. This signal is conveyed through the wireless and wired portions of the system informing all involved transmission nodes that the stream of packets carrying voice from the active user has ceased. Failure to receive the end of transmission signal at a node in the network may cause the node to take inappropriate actions or fail to take appropriate actions. Such a problem is especially acute where a node hinders further communications by other users due to the failure to receive an end of transmission signal. Thus, there exists the need for an improved method for minimizing problems associated with the lack of receipt of an end of transmission signal in a packet system.